Such a blower apparatus for cooling incorporated into a vehicle is used for cooling the engine or recently for cooling the battery of an electric vehicle for instance. An engine-cooling blower apparatus for instance continues its rotation for a certain period of time using a timer even after the engine is stopped, to blow and cool the engine if the engine coolant is still hot. Such a cooling operation after the engine is stopped, however, causes a current to continue flowing through the control circuit for a cooling operation in spite of the fact that the ignition switch has been turned off, which can cause a dead battery. Such a current that flows when an ignition switch is off is called dark current.
Under such circumstances, a circuit has been devised for controlling a cooling fan for a vehicle engine so as to rotate the fan for a certain period of time even after the ignition switch is turned off, while reducing dark current (refer to PTL 1 for example).
The circuit for controlling an engine cooling fan described in PTL 1 includes a thermal switch and a timer, where the thermal switch outputs a fan motor drive signal when the temperature of engine coolant is higher than a set level; and the timer times a given period of time after the ignition switch is turned off. This control circuit drives the fan motor when a fan motor drive signal is output, and stops driving the fan motor when the given period of time has elapsed. This cools the engine using the fan motor even after the engine stops when it is hot. When the ignition switch is turned off and the given period of time has elapsed, the control circuit cuts power to the thermal switch to eliminate dark current due to the thermal switch.
PTL 2 discloses an in-vehicle apparatus that includes a circuit for preventing an inrush current to a smoothing capacitor in a power supply.
For an existing control circuit of an engine-cooling fan described in PTL 1, the power supply remains connected to the timer after the ignition switch is turned off so as to operate the timer. This causes a small amount of current as dark current to flow through the timer even if the ignition switch has been turned off, which means that dark current is cut off incompletely.